Preparation

Make broth and filling while dough stands:
Cut off asparagus tips, then halve each tip lengthwise and reserve.

Bring stock, cheese rind, and bay leaf to a simmer in a medium saucepan, then add asparagus stems and cook, uncovered, until stems are just tender, 5 to 6 minutes. Transfer stems to paper towels and cool slightly. Reserve broth.

Purée asparagus stems in a food processor with grated parmesan, mascarpone, bread crumbs, zest, and 1/2 teaspoon each of salt and pepper.

Make Ravioli:
Cut dough into 4 equal pieces. Cover 3 pieces with plastic wrap, then pat out remaining piece into a flat rectangle and generously dust with flour.

Set rollers of pasta machine on widest setting. Feed rectangle, a short side first, through rollers. Fold rectangle in thirds, like a letter, and feed it, a short side first, through rollers. Repeat 6 or 7 more times, folding dough in thirds and feeding it through rollers, a short side first each time, dusting with flour to prevent sticking.

Turn dial to next (narrower) setting and feed dough through rollers without folding, a short side first. Continue to feed dough through without folding, making space between rollers narrower each time, until the second- or third-narrowest setting is used. (Do not roll too thin or pasta will tear when filled.)

Put pasta sheet on a lightly floured kitchen towel (not terry cloth) with a long side nearest you. Drop 6 rounded teaspoon-size mounds of filling 10 inches apart in a row down center of right half of sheet. Brush pasta around mounds of filling lightly with water, then lift left half of sheet and drape over mounds.

Press down firmly but gently around each mound, forcing out air. (Air pockets increase the chance that ravioli will break during cooking.) Cut pasta (between mounds) with a sharp knife into roughly 2-inch squares. Line a large shallow baking pan with a lightly floured kitchen towel (not terry cloth), then arrange ravioli in 1 layer in it. Make more ravioli with remaining pieces of dough and remaining filling, transferring to lined pan.

Cook ravioli and Asparagus tips:
Bring a pasta pot of salted water (2 tablespoons salt for 6 quarts water) to a boil over high heat, then reduce heat to a gentle boil.

Add half of ravioli to gently boiling water, carefully stirring to separate, and cook, adjusting heat to keep at a gentle boil, until pasta is just tender, 2 to 3 minutes. Lift cooked ravioli with a slotted spoon, draining well over pot, then transfer to bowls with broth. Repeat with remaining ravioli.

Cooks' note:
Filling and broth, without asparagus tips, can be made 1 day ahead. Chill separately, uncovered, until cool, then covered.